```python
from fastapi import FastAPI
import helpers
import asyncio

app = FastAPI()

@app.get("/portfolio")
async def portfolio(symbols: str):
    # Parse the comma‑separated list of symbols
    symbol_list = [s.strip().upper() for s in symbols.split(",") if s.strip()]
    # Fetch all prices concurrently using the async helper
    prices = await asyncio.gather(*[helpers.afetch_price(sym) for sym in symbol_list])
    # Build the response dictionary
    result = {sym: price for sym, price in zip(symbol_list, prices)}
    return {"prices": result}
```